Republican Sen. Marco Rubio's manufactured outrage over President Barack Obama's leaked immigration proposal illustrates the GOP's dilemma: They have to sound like they're doing battle with this president even when they agree with him.

A draft of the White House immigration proposal leaked to USA Today says the administration would offer a new visa that would allow undocumented immigrants to stay and work in the U.S. legally for four years, with an option for an extension.

They could earn an eight-year window to apply for permanent residency if they learn English, U.S. history and pay back taxes. The proposal also calls for enhancements to border security and more immigration judges. Obama administration officials also have said the White House would only submit its bill if bipartisan efforts in Congress fail to produce anything.

But Rubio, one of the "Gang of Eight" senators working on a bipartisan immigration bill, did not hesitate to shoot down the president's proposal as "half-baked," "seriously flawed" and "dead on arrival" if it is proposed to Congress.

That's curious since it is hard to make out a glimmer of daylight between the Obama proposal and Rubio's own stated positions. The main difference between their plans appears to be Rubio's enforcement trigger. Both plans call for border improvements, but only Rubio has demanded more border security before the citizenship program kicks in.

As he told conservative radio host Rush Limbaugh last month, "If, in fact, this bill does not have real triggers in there, if there is not language in this bill that guarantees that nothing else will happen unless these enforcement mechanisms are in place, I won't support it."

Which raises a critical question: After all the millions of dollars that have been spent on more fences, border guards and equipment, how secure do the borders have to be before Republicans are satisfied that they're "secure"? For some conservatives, that's like asking how much evidence they need before they believe President Obama's birth certificate is authentic.

Republicans in general don't want to open any path to citizenship for illegal immigrants until certain border security measures are in place — even though almost half of the nation's undocumented workers arrived legally but overstayed their visas, according to a Pew Hispanic Center study.

Nevertheless, Rubio, a 41-year-old son of working-class Cuban exiles and an anticipated 2016 presidential contender, can't drift too far ahead of his party on this issue.

Sure, Republicans are trying hard to recover support from Hispanic voters who, compared to their 2004 turnout for President George W. Bush, abandoned the party in large enough numbers to clinch Obama's re-election. But comprehensive immigration reform, as popular as it may be in Latino communities, still deeply divides Republicans, especially at a time when even right-wingers fear potential primary fights with further right-wing challengers.

So it only helps Rubio win valuable support if he appears to be in no way in cahoots with Obama, even when their immigration proposals sound like identical twins.

That won't be easy. Alabama Republican Sen. Jeff Sessions issued a news release bashing the leaked Obama plan as "little different in its substance from the Gang of Eight plan" and perhaps "the beginning of the collapse of this new scheme to force through a fatally flawed plan." Limbaugh added a paranoid note by suggesting Rubio and the rest of "our guys" will get saddled with an unpopular reform plan while Obama gets what he wants anyway.

With the camouflage wearing thin, Rubio is left with little recourse but to play along with his party's nearly exhausted "Party of No" strategy: Show a willful blindness to the Obama they see as they badmouth the mythical Obama they have made up.

You remember him. The invisible Obama to whom Clint Eastwood spoke in the empty chair he brought onstage at the Republican National Convention. He's the secret Muslim/Kenyan who hates America and tries to divide the races and ethnics against one another.

He's the Obama with whom a number of Republican leaders agree, but they don't dare admit it.

Clarence Page is a member of the Tribune's editorial board and blogs at chicagotribune.com/pagespage.